1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that forms an image by causing a toner, which has been made to fly from a toner carrier, to adhere to recording medium means by being flown via toner passage holes, the opening and closing of which are controlled.
2. Description of the Related Art
An image forming apparatus of the type that directly records an image on a recording medium (comprising an intermediate recording medium) using toner (a recording material), which is called toner jet, direct toning, toner projection and the like, is known as a conventional image forming apparatus.
For example, Examined Utility Model Application Publication No. H5-29479 (referred to as Prior Art 1) discloses a configuration, which has a grid electrode disposed by way of an insulating layer between a toner container and a control member comprising a pair of electrode plates, and which forms an image by applying an alternating voltage to the grid electrode to convert the toner into a cloud. This configuration makes possible image formation without the need for an exposure optical system and electrostatic latent image, but, in principle, is not able to avoid the adherence of toner to the electrode plates of the control member, and the buildup of toner on the electrode plates gives rise to a dramatic drop in control performance.
Japan Patent Laid-open Publication No. S57-198470 (referred to as Prior Art 2) discloses a configuration in which a grid electrode is disposed between a toner carrying surface and a latent image carrying surface, and a toner cloud is formed by applying an alternating current voltage between the grid and toner carrying surface. In this configuration, it is possible to make the latent image carrying surface spacing sufficiently larger than that of the so-called jumping development system, which applies an alternating current bias between the toner carrying surface and the latent image carrying surface, and although a toner cloud is capable of being formed without affecting the development bias condition, it remains within the domain of the conventional image forming apparatus in that it requires an exposure optical system and an electrostatic latent image.
Japan Patent Laid-open Publication No. S63-136058 (referred to as Prior Art 3) discloses an image forming apparatus that uses frictional electrification between either fixed plates or rotating rollers to apply an electrification charge to toner supplied from a toner hopper, and after rotational feeding, controls the flight of the toner with an electric field between a control pulse applied to a control member and the rotating rollers. Toner having an electrification charge is electrostatically adhered to the surface of the rotating roller here, and this toner must be separated using a control pulse. This is problematic in that, since there is a gap of several hundred micrometers or more between the rotating roller and the control member, the control pulse applied for separation must inevitably have a high voltage of 500 V or more, and the cost of the driver needed to control the number of picture elements is extremely expensive. Another problem is poor responsiveness and time delays associated with causing the toner adhered to the rotating roller to separate and fly.
Japanese Patent 2933930 (referred to as Prior Art 4) and Japanese Examined Patent Application Publication No. H2-52260 (referred to as Prior Art 5) disclose an image forming apparatus that applies a control pulse to a control electrode through which the developer passes, while applying an alternating bias between a rotating developer support and control means. Although this configuration alleviates the problem of responsiveness associated to the apparatus disclosed in the above-mentioned Prior Art 3, a uniform alternating field is applied to the entire flying area of the toner, and the flying state and time that the developer is adhered to the developer support are repeated. For this reason, a strong alternating bias must be applied for separating the developer that is adhered to the developer support, causing a major reliability problem in that there is no way to avoid the separated toner flying with great force to control means side, and large amounts of developer adhering to the control means electrode. Furthermore, this configuration cannot solve the problem of driver cost since the same gap as mentioned hereinabove exists between the developer support and control means, and the voltage value applied between the two is high (500 V or more), requiring that the control pulse for forming the field that either passes or blocks the developer to/from this field be a similarly high voltage value.
By contrast, Japanese Patent Laid-open Publication No. S59-181370 (referred to as Prior Art 6) discloses a configuration, which has a plurality of electrodes in a developer carrier, and causes the toner to fly to the control electrode side by forming a temporally changing electric field between these electrodes. Since the passage of toner that is flying and floating in the proximity of the control electrode is controlled here, the problem of the high control voltage of the apparatuses of Prior Art 3 through Prior Art 5 is resolved.
Japan Patent Laid-open Publication No. H02-226261 (referred to as Prior Art 7), similar to the above Prior Art 6, discloses a configuration, which has a plurality of electrodes in a developer carrier, and which causes the toner to fly by forming a temporally changing electric field between these electrodes, and a control electrode for controlling the passage of the toner, which had heretofore been installed on the recording medium side, is installed on the toner supply side. It is disclosed that in this configuration, the control voltage, which had to be 400 V in the conventional apparatus, may be 100 V, and when the toner that adheres to the print head, on which the control electrode is provided, is removed, this toner may be returned to the toner supply source.
Further, Japanese Translation of PCT Application No. 2001-505146 (referred to as Prior Art 8) discloses a configuration, which uses a rotating cylindrical sleeve to supply toner, and which applies an electrostatic force that allows the toner to pass through an aperture via a uniform electrical field between the print head surface potential and the sleeve, provides a deflecting electrode that is paired on the print head surface side with the control electrodes surrounding the aperture, and raises the print dot density in the main scanning direction. It is disclosed that a guard electrode is disposed between the control electrodes that control the passage of the toner here to prevent interaction between the control fields.
Japanese Patent Laid-open Publication No. H11-301014 (referred to as Prior Art 9) discloses the disposition of a control electrode, which supplies toner via a toner supply roller, and which controls the flight of the toner on the toner supply roller side of the aperture containing member, and a deflecting electrode, which deflects the flight path of the toner.
Such direct recording-type image forming apparatuses proposed in the past have numerous problems that need to be solved, such as those described above.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-open Publication No. H06-005396.